Known illumination arrangements wherein the light source comprises a light-emitting diode or a laser diode, is often used for general illumination or background illumination for liquid-crystal displays (LCD). Herein, the optical waveguide directs light, emitted by the coupled light source, out from the optical waveguide at a waveguide end or at a centrally located window. In the latter example, the surface of the optical waveguide is structured in the window region, e.g. by knobs, grooves, or by some other roughening in order to homogenize the light exit. The optical waveguides are composed of transparent material, such as epoxy resin or polymethyl methacrylate (PMMA). In the course of guiding the light and its internal reflections, it is desirable to have as little light loss as possible, while maintaining cost-effective production and practical and simple assembly.
A related art embodiment is shown in FIG. 5. Here, a light-emitting diode 50 (LED) is coupled into an optical waveguide 51 which in turn is plugged into a mount 52a, 52b. The mount 52 and LED 50 are mounted on a printed circuit board (PCB) 53. The light emitted by the LED 50 is internally reflected at bevel 54. For production engineering reasons, in particular in favor of ease of assembly, the bevel 54 is not covered with a reflective material. During the internal reflection of light at bevel 54, angled preferably at 45°, light necessarily emerges from the optical waveguide. This light is lost for the envisaged application since it is not guided any further in the optical waveguide. On the other side, the mounts 52a, 52b simultaneously serve as reflectors which prevent light from emerging from the optical waveguide 51 on these sides. When observing the surface of the optical waveguide from the direction B, for example when the optical waveguide is embodied as LCD background illumination, some regions on the optical waveguide surface appear brighter than others (hot spots) as a result of the light internal reflection at the boundary surface 54 and the direct radiation of the light source. Hot spots are bright surface regions which appear in a light exit window and cannot be corrected by the surface configuration of the optical waveguide in the light exit window. Producing a special reflector for the inclined surface 54 in the form of an injection-molded part is costly and undesirable.